In a convenience sample of hospital visitors, researchers found that epilepsy was significantly more common among first-degree relatives of patients with bipolar disorder than among controls. Likewise, the rate of bipolar disorder was significantly increased among relatives of epilepsy patients.
This implies “genetic or/and environmental relationships between the two disorders”, say study author Mohammed Jidda (University of Maiduguri, Nigeria) and co-workers in the Journal of Affective Disorders.
The team recruited 60 first-degree relatives of epilepsy patients, and asked them to complete the Mood Disorder Questionnaire. Based on the responses, 14.5% had bipolar disorder, compared with just 2.1% of 50 control hospital visitors who did not have a first-degree relative with bipolar disorder or epilepsy.
In addition, 15.2% of 40 first-degree relatives of bipolar disorder patients had epilepsy, assessed by applying International League Against Epilepsy criteria to the participants’ responses to a predesigned questionnaire. By contrast, just 2.0% of the control group were judged to have epilepsy.
The researchers caution that, although the findings are in line with other studies, their research was preliminary and hospital-based, and did not account for many potentially confounding environmental factors and behaviours.
They conclude: “Large family studies of multiple first-degree relatives of bipolar disorder and epilepsy (prelude to twin or/and gene studies) should be conducted to confirm the etiological overlap between the two disorders, resulting from a shared genetic susceptibility.”